Vania



J. BECKER.

AMMONIA, TAR,AND BENZOL RECOVERY PROCESS.

APPLICATION FILED Aumz, ma.

Patnted June 24, 1919.

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, UNITED STATES OFFICE.

JOSEPH BECKER, on PITTSBUIR-GH, PENNSYLVANIA, ASSIGNOR TO THE KOPPEBS comm, or PITTSBURGH, PENNSYLVANIA, A conrom'rron or. PENNSYL- V'ANIA.

Specification of Letters Patent. Patented June 24 1919 Application filed August 12, 1918. Serial No. 249,379.

, provement in Ammonia, Tar, and Benzol Recovery Processes, of which the following is a specification.

My invention relates primarily to the recovery of tar and ammonia, and of .benzol, and its homologues, from coke-oven gas, and has for an object a simplified and eflicient extraction of the tar, and also a recovery of the ammonia by a method that simplifies apparatus and economizcs the heat required in the ammonia recovery and has for a further object the recovery, directly from the gas, of a portion of benzol, and its homologues, that is carried off dissolved in the tar in the usual methods of tar-extraction from the gas, and the invention may also be applicable to the treatment of gas that is otherwise derived from the carbonization of coal, and may also have such other objects and results as are found toobtain in the processes hereinafter set forth and claimed.

In the accompanying drawings, Figure 1 is a conventional diagram illustrating an embodiment of the invention in a preferred arrangement of apparatus for practising its processes; and Fig. 2 is a'key to the symbols employed in the various lines that show the connections between the apparatus indicated in Fig. 1.

5 indicates the coke-ovens from which the coke-oven gas is derived. The gas flows first into an electrical precipitator 6, which it enters at a temperature of about 80 C. At such temperature the tar-is carried in the gas in the form of a finely comminuted mist,

and such mist is effectively precipitated in the electrical precipitator, from which the precipitated liquefied tar is drained off into the tar-tank 7. The water and ammonia are carried through the precipitator in the form of vapor-,'as the gas leaves such precipitator at a temperature that is still above the water saturation point of such gas. The gas is then conducted to and enters the hot acidwasher tower 8, in which the ammonia is absorbed by the acid-solution that is kept hot by the absorption reaction. The gas both enters and leaves the acid-washer with a temperature that is still somewhat above its water saturation point, but so little above that fpractically no water is taken up by the gas rom the acid-solution and consequently therev is "no precipitation of ammonium sulfate in the acid-washer tower and the gas leaves itstill carrying as vapor substantially the original water content with which such gas left the ovens. The acid-solution from the said acid-washer tower 8 flows into a saturator 9, carrying with it into the saturatorany slight amount of ammonium sulfate that may havebeen precipitated. The acid-solution drained from the saturators drain table 10 and centrifugal drier 11, into the mother-liquor tank 12, is forced back, by the acid pump 13, to the top of the acid-washer tower 8, a proportion of fresh acid being there continuously added from the acid-tank 14. A portion of the acid-s0- lution from the mother-liquor tank 12 may also flow back into the saturation-bath in the saturator 9. From the acid-washer tower the gas flows into and through the cooler 15 that is sprayed with fresh water from thewater tank 16.v The drain from this cooler flows to the naphthalene recovery apparatus. The gas issues from the cooler 15 at a temperature of about 30 (1., substantially dehydrated, and having been previously freed of its tar and ammonia. Such gas passesnext through the exhauster 17 and thence is forwarded in part directly to the saturator, through the gas-line 18, and

in-part through the ,by-pass 19 into the gaslinethat leads from the saturator to the final cooler 20. The gas passing from the exhauster into the saturator has a temperature of about 35 (1., and discharging through the saturation-bath it effects the evaporation-requisite to precipitate the ammonium'sulfate from the bath. The gas issuing from the saturator, at a temperature of about 45 0., passes, as just above mentioned, to the final cooler 20', together with the gas coming directly through the aforesaid by-pass 19 from the exhauster. This final cooler 20 is constantly sprayed with fresh water from the before-mentioned watertank 16, and the drain from said cooler is carried to the naphthalene recovery apparatus through the naphthalene drain line 21. The gas issues from the final cooler 20 cooled to about 20 (3., still-carrying substantially its entire original content of benzol and its homologues, and then passes into the benzol scrubber 22, in which the benzol and its homologues are extracted by a constant flow of straw oil entering the scrubber through the oil line 23. The benzolized oil drains from the scrubber 22 into the benzolized oil line 24 leading to the further apparatus for the recovery of such benzol and its homologues. The gas from the benzol scrubber passes to the gas-holder 25 and thence to its final distribution, in part back to the ovens to be used as the fuel-gas for their firing, and in part to whatever other service iuch clean coke-oven gas may be employed or.

The taking out of all of the tar while the gas is still hot, and by a precipitation method that does not require the gas to pass through absorption films or sprays of tar, saves the absorption of benzol, and its homologues, that occurs when the gas is either cooled to effect tar extraction or passed through films or sprays of liquefied tar, and there is thus a substantial increase in the final recovery of benzol and its homologues directly from the gas.

The tar recovery is complete and is substantially free of admixture of other condensate. And the ammonia is effectively and completely taken out in the acid washer, and the ammonium sulfate is precipitated in the saturator with gas that has not undergone any reheating operation other than the heating incidentally derived from the adiabatic compression to which it is subjected in passing through the exhauster. The naphthalene is taken off with the drainage from the first cooling operation to which the gas is subjected, but this cooling operation is subsequent to both the tar precipitation and the, ammonia absorption, both of which are effected while the gas is still at high temperature; and so na hthalene stoppages in the apparatus are e ectively avoided.

The processes of the invention may be practised in various ways, other than the particular embodiment that has been described for purposes of illustration, and still be within the scope and subject matter of the claims hereinafter made.

In my co-pending application Serial No. 249,378, filed of even date with the present application, I haveset forth and directed claims to the general process of absorbing the ammonia from the hot gas passing!- through an acid-wash and then leading the hot ammonia-charged acid-solution into a saturation bath through which the ammonia-freed and relatively low-temperature gas is passed and carries off the evaporation from such bath.

I claim:

1. In 'a process for the recovery of tar and ammonia from coke-oven gas, the combination of steps that consists in: extracting the tar from the coke-oven gas hot; passing such hot gas through an acid-wash to absorb the ammonia of the gas; discharging the mother-liquid from such acid-wash into .a saturation-bath; passing the tar-free and ammonia-free gas through a cooling and dehydrating operation; and passing such gas through said saturatiombath, to effect deposition of the ammonium sulfate; substantially as specified.

2. In a process for the recovery of benzol and its homologues from coke-oven gas, the combination of steps that consists in: electrically precipitating the tar residue from the gas while the latter is still hot enough to preclude appreciable absorption of benzol by the tar precipitated; and then passing the gas through ammonia recovery and benzol ex traction operations; substantially as speci- 3. In a process for the recovery of tar, ammonia and benzol, and its homologues, from coke-oven gas, the combination of steps that consists in: electrically precipitating the tar residue from the gas while the gas is enough superheated substantially to preclude the tar from absorbing the benzol, and its homologues, in the gas; passing the tarfreed gas through an ammoniaabsorbing acid-solution at a temperature above the water-saturation point of the gas but low enough to preclude substantial deposition of ammonia sulfate in said solution; conducting said ammonia-charged solution into a saturation-bath; dehydrating said ammonia-freed gas and then passing it through said saturation-bath to effect deposition of the ammonium sulfate; and then passing said gas to the further operations for the recovery of benzol and its homologues; substantially as specified.

4. In a. process for the recovery of benzol and its homologues from benzol charged gas, the combination of steps that consists in: electrically precipitating the tar residue from the gas while the latter is still hot enough to preclude appreciable absorption of benzol by the tar precipitated; and then passing the gas through the further operations requisite to the recovery of the ammonia and the benzol; substantially as specified.

5.. In a process for the recovery of tar, ammonia and benzol, and its homologues, from gas charged with them, the combination of steps that consists in: electrically precipitating the tar residue from the gas while the gas is enough superheated substantially to preclude the tar from absorbing the benzol, and its homologues, in the gas; passing the tar-freed gas through an ammonia-ab- 'sorbing acid-solution at a temperature above the Water-saturation point of the gas but low enough to preclude substantial deposition of ammonium sulfate in said solution; conducting said ammonia-charged solution into a saturation -bath; dehydrating said ammoniafreed gas and then passing it through said saturation-bath to eifect deposition of the ammonium sulfate; and then 10 passing said gas to the further operations for the "recovery of ben'zol and its homo- JOSEPH BECKER.

Witnesses: I

HENRY LOVE CLARKE, JOSEPH DVORAK. 

